Parasite fauna of two sympatric silversides species (Odontesthes smitti and O. nigricans, Atherinopsidae) on the Patagonian coast. 7th International Symposium on Fish Parasites, Viterbo, Italia

CARBALLO, M. CECILIA; DIAZ, J.I.; GARBIN, L.E.; CREMONTE , FLORENCIA; NAVONE, GRACIELA T

Viterbo, Italia

Simposio; 7th International Symposium on Fish Parasites; 2007

Odontesthes smitti and O. nigricans (Pisces: Atherinopsidae) are important item preys to fishes, birds and marine mammals from Patagonian coast Argentina, which make them in a potential intermediate hosts for helminthes. Moreover, its populations overlap and compete for food resources. In this work we present the results of the first study about parasitic fauna from two species of Odontesthes from north patagonic gulfs. From April 2003 to March 2005, 183 O. smitti were caught in Nuevo gulf (NG) (42°47’S, 65°02’O) and 173 in San José gulf (SJG) (42°25’S, 64°07’O); 94 O.nigricans in NG and 20 in SJG. The fishes were fixed with 5% and parasites were recovered and identified at the most precise taxonomic level possible. Sixteen parasite species were found: 1 Microsporidea (Protozoa); 1 Cestoda: Scolex polymorphus larvae (Tetraphylidea); 5 Digenea: metacercariae Prosorhynchoides sp. (Bucephalidae), Lecithaster sp., Aponurus sp. (Hemiuridae), Proctotrema sp. (Monorchiidae), Diphterostomum sp. (Zoogonidae); 5 Nematoda: Cucullanus marplatensis (Cucullanidae), Huffmanela moraveci (Trichosomoididae), 1 larvae indet. (Acuariidae), 2 larvae indet (Anisakidae); 2 Acantocephala: cystacanth larvae indet. (Polymorphidae), adult family indet.; 2 Copepoda: Bomolochus globiceps (Bomolochidae), Peniculus sp. (Penelidae). In O. smitti from SJG all the mentioned species were found, while in NG specimens microsporideos were not found. In O. nigricans from NG 14 of these species were found, being absent S. polymorphus and Aponurus sp. In O. nigricans from SJG, these two last helminthes species, one of anisakid larvae and the microsporidea were absent. The prevalence (P) and mean intensity (MI) were high in O. smitti from both localities (98-99% and 118- 220 respectively). The P in O. nigricans was also high (84-100%) while MI was lower (23-30). The maximum richness (S) found at infracommunity level was 5 inO. nigricans from GSJ and 7 from the rest of component communities. However, the more common infections was constitute for 2 and 4 species in O. smitti (31-33%) and 3 and 5 inO .nigricans (18-35% of infracommunities). In O. smitti the diversity and evenness were constant in both gulfs (H’=0.8 and E=0.3), while this values were higher for O. nigricans in SJG and NG (H’=0.96-1.53 and E=0.4-0.6 respectively). These results indicate that not exist marked differences in the specific composition of parasites communities from both host species. Also it indicates that both species play similar roles within food webs in the region. The low values of H’ and E found in O. smitti indicate that some species are presented in higher intensity than others. In O. nigricans, although a low richness was observed, the highest H’ and E values reflect a community with species uniformly represented.